Bolbophorus Damnificus Research Articles

Copper Toxicity to the Ghost Rams‐Horn Snail Biomphalaria havanensis

AbstractAvian piscivores cause direct economic losses to the aquaculture industry through predation, as well as indirect losses through transmission of digenetic trematodes. Bolbophorus damnificus is a trematode parasite associated with significant losses in catfish aquaculture. The complex life cycle involves the American white pelican Pelecanus erythrorhynchos, planorbid snails, and ictalurid catfish. With no approved therapeutics for B. damnificus in catfish Ictalurus spp. and federal protections on American white pelican, management is restricted to controlling snail hosts. Two snail species, marsh rams‐horn snail Planorbella trivolvis and ghost rams‐horn snail Biomphalaria havanensis, are common inhabitants of commercial catfish ponds and known to transmit B. damnificus. Previous work evaluated copper sulfate toxicity on marsh rams‐horn snails; however, data are lacking for ghost rams‐horn snails. Herein, laboratory‐reared adults of ghost rams‐horn snails and marsh rams‐horn snails were exposed to copper concentrations ranging from 0.16 to 3.38 mg/L Cu to evaluate 24‐, 48‐, and 72‐h acute toxicity. Additionally, sequential low‐dose treatments ranging from 0.1 to 0.8 mg/L Cu were evaluated on eggs, juveniles, and adults of ghost rams‐horn snails as a potentially safer treatment regime for ponds. Acute toxicity was similar between snail species for all exposure times. A 72‐h exposure produced an LC50 of 0.10 and 0.37 mg/L Cu for ghost rams‐horn snails and marsh rams‐horn snails, respectively. The LC50 values increased to 1.1 mg/L Cu for both species with 48‐h exposure. However, in the multiple low‐dose study, a single dose of 0.4 or 0.8 mg/L Cu was lethal to all adult snails after 1 week, as was 0.2 mg/L Cu after two doses. Four doses of 0.1 mg/L Cu or greater killed all ghost rams‐horn snail juveniles. Results indicate that marsh rams‐horn snails and ghost rams‐horn snails have similar sensitivity to copper, and multiple low‐dose treatments were effective against all life stages of ghost rams‐horn snails. These data indicate that copper can be an effective treatment for snail control in commercial catfish ponds.

Physiological response of channel (Ictalurus punctatus) and hybrid (I. punctatus x I. furcatus) catfish following Bolbophorus damnificus infection

The trematode Bolbophorus damnificus is associated with reduced production in farm-raised catfish in the southeastern United States. Previous research demonstrated that even mild outbreaks, which may go unnoticed by producers, can result in >60% reduction in net return due to decreased feeding and trematode-induced mortality. While infectivity rates in channel (Ictalurus punctatus) and hybrid catfish (I. punctatus x I. furcatus) are similar, hybrid catfish experience lower mortality when exposed to comparable numbers of Bolbophorus cercariae than channel catfish cohorts. This study compared physiological responses in channel (21.4 ± 0.93 g) and hybrid (27.5 ± 2.63 g) catfish fingerlings exposed to 450 cercariae/L. Fish were sampled over the next 49 days for hematocrit, hemoglobin, red blood cell (RBC) concentration, plasma glucose, plasma lactate, and plasma osmolality. Exposed channel and hybrid catfish experienced a dramatic drop in hematocrit, hemoglobin, and RBC concentration during the peak mortality window associated with metacercarial development, but recovered afterwards, suggesting an anemic response to the development of the parasite and subsequent recovery once metacercarial encapsulation is complete (∼15 days post-exposure). There were no differences over time in any of the plasma parameters measured, but there was an overall decreased osmolality in both exposed groups, suggesting a prolonged low-level stress response to infection. There was high mortality in the exposed channel catfish groups from days 9 to 15 post-infection, consistent with previous studies. Comparably, hybrids appeared healthy and active throughout the trial with only negligible mortality. In all trials, infected fish presented clinical signs consistent with B. damnificus infection and all exposed fish had visible metacercariae below the skin. There was a substantial anemic response in both catfish types, suggesting the physiological response to B. damnificus infection may not differ between channel and hybrid catfish and the significant differences in mortality may be attributed to survivor bias, hybrids greater tolerance of the anemic state or other unidentified factors. The biological and economic implications of these findings are unclear, but the behavioral differences observed between the two fish groups in reponse to B. damnificus, coupled with reduced mortality in hybrids, supports previous work indicating hybrids are more tolerant of B. damnificus infection and outbreaks in hybrid catfish may not yield the same deleterious effects as channel catfish.

CERCARIAL LONGEVITY AND INFECTIVITY OF BOLBOPHORUS DAMNIFICUS, WITH NOTES ON METACERCARIAL PERSISTENCE AND SITE SPECIFICITY IN CHANNEL AND HYBRID CATFISH.

Advances in hybridization practices in U.S. catfish aquaculture have led to increased production of channel (Ictalurus punctatus) × blue catfish (Ictalurus furcatus) hybrids to capitalize on their more favorable production characteristics. However, the effects of typical channel catfish pathogens on hybrids are not well understood, including the digenean Bolbophorus damnificus, which has caused significant losses in channel catfish production. Three experiments were conducted to assess the longevity and site specificity of 2 life stages of B. damnificus impacting catfish production. The first experiment investigated the cercarial longevity and infectivity of B. damnificus over time. Channel catfish were individually challenged with 100 cercariae/fish with cercariae aged in 12-hr time intervals over 5 days (n = 5 fish/time point), with metacercarial cysts excised and enumerated 14 days postchallenge. There was a decrease in cercaria viability and encysted metacercariae over the first 36 hr, with the 12-hr time point having both the greatest cercaria survival and the highest number of metacercariae in exposed fish. The second experiment investigated the longevity of metacercariae within both channel and hybrid catfish. Fish (n = 30) were exposed to 2 treatments (75 or 150 cercariae/fish), and 2 fish from each treatment were sampled every 3 mo for 13 mo. Live metacercariae, based on motility observed after excystment, were found in both species up to 13 mo postchallenge, indicating the metacercariae of B. damnificus can persist throughout an entire growing season in both channel and hybrid catfish. The third experiment investigated the site specificity of metacercariae within both channel and hybrid catfish. Fish (n = 60/species) were challenged with 300 cercariae/fish and 9 fish/species were sampled after 90 days. Metacercariae were excised and enumerated from the anterior midsection (head and body), posterior midsection (trunk/caudal peduncle), ventral (belly), and caudal fin (tail) sections of each fish. Overall, the trunk/caudal peduncle had a 2-fold increase in the number of metacercariae excised, and although not significantly higher, results indicate this region should be the focal point of pondside assessment for the presence of B. damnificus because of ease of detection of encysted metacercariae.

Comparative Mortality of Juvenile Channel and Hybrid Catfish Exposed to Bolbophorus damnificus Cercariae

AbstractThe trematode Bolbophorus damnificus (Digenea: Bolbophoridae) has caused significant economic losses since the late 1990s, with deleterious effects on production efficiency in farm‐raised catfish. Previous work has demonstrated that even mild outbreaks, which may go unnoticed by producers, can result in over 60% reduction in net economic returns. Although transmission rates in Channel Catfish Ictalurus punctatus and hybrid catfish (Channel Catfish × Blue Catfish Ictalurus furcatus) are similar in controlled studies, anecdotal industry reports imply that the impacts of B. damnificus on hybrid catfish are less severe. In this study, mortality in juvenile Channel and hybrid catfish exposed to B. damnificus was evaluated in two discrete, replicated infectivity challenges. Mortality curves in Channel and hybrid catfish were consistent with trends previously established for B. damnificus in Channel Catfish, although in both challenges cumulative mortality was significantly lower in hybrids. All exposed fish presented clinical signs consistent with B. damnificus infection—namely lethargy, exophthalmia, distended abdomens, and metacercariae grossly visible below the skin. No mortality occurred and no parasites were observed in control fish. The biological and economic implications of these findings on catfish production are unknown but suggest that hybrid catfish are less susceptible to the deleterious effects and reduced productivity elicited by B. damnificus in Channel Catfish.

Assessment of Bolbophorus damnificus prevalence and cercariae shedding in Planorbella trivolvis populations from catfish aquaculture ponds in Mississippi, USA

AbstractBolbophorus damnificus (Digenea: Bolbophoridae) causes significant losses in US catfish aquaculture. Little is known regarding the prevalence of infected snail hosts during outbreaks. To assess prevalence of snails observed shedding Bolbophorus spp. cercariae, as well as snails that were infected but not observed shedding cercariae, Planorbella trivolvis (n = 8,159) were collected from 14 catfish production ponds with B. damnificus activity in Mississippi, USA. Individual snails were placed in 10 ml of filtered (20 μm) reservoir pond water and observed for 48 hr for cercariae release. Identification of B. damnificus or Bolbophorus sp. type II cercariae was confirmed by duplex PCR. Genomic DNA was isolated from ~100 non‐shedding snails from each pond and the PCR assay used to identify the presence of B. damnificus or Bolbophorus sp. type II infected snails. The prevalence of snails shedding B. damnificus ranged from 0.23 to 13.6%. Observation of cercariae shedding underestimated true B. damnificus and Bolbophorus sp. type II prevalence in 42.9 and 64.3% of sampled ponds, respectively. Prevalence of B. damnificus infected snails was typically <3%, indicating numbers of infected snails during outbreaks are low and mitigation efforts may be successful simply by reducing snail numbers and not require complete eradication.

Encapsulation of Bolbophorus damnificus (Digenea: Bolbophoridae) Metacercariae in Juvenile Channel Catfish, Ictalurus punctatus, Is Linked to Delayed‐onset Mortality

AbstractBolbophorus damnificus (Digenea: Bolbophoridae) causes significant economic losses in catfish aquaculture in the southeastern USA. To determine mortality trends associated with B. damnificus exposure, three separate disease challenges were conducted. The first challenge exposed channel catfish, Ictalurus punctatus, fingerlings (7–13 cm) to approximately 285 B. damnificus cercariae/L, while the second exposed fish to approximately 215 cercaria/L. Fish were monitored for morbidity and mortality for 28 d. In both studies, mortality first occurred 8 d postchallenge (PC) and peaked at 9 and 10 d PC, respectively. Mortality had subsided by 14 d PC, with only sporadic mortality occurring >15 d PC. Dead and moribund fish presented with lesions consistent with B. damnificus infection. A third challenge was performed to record histological changes associated with parasite development from initial exposure up to the cessation of mortality. Catfish (2–5 cm) were exposed as described above to a range covering 0, 35, 70, 100, 150, 175, and 215 cercariae/L. Each day, two fish were sampled from each treatment. Mortality trends were consistent with previous challenges. The mortality window coincided with parasite encapsulation, neovascularization, and development of the host‐derived cyst, suggesting that morbidity and mortality are linked to host pathophysiological changes in response to metacercariae encapsulation.

Biomphalaria havanensis is a Natural First Intermediate Host for the Trematode Bolbophorus damnificus in Commercial Catfish Production in Mississippi

AbstractThe digenetic trematode Bolbophorus damnificus is a significant hindrance to the production of farm‐raised catfish in the southeastern USA. Severe infections with Bolbophorus damnificus can result in death, but the real damage lies in mild to moderate infections, which can go unnoticed by producers. Research has shown even mild infections can inhibit production to the point of operating at a net loss. The ramshorn snail Planorbella trivolvis is the first intermediate host for Bolbophorus damnificus and is prevalent in most commercial catfish ponds in the Southeast. Management practices aimed at controlling Bolbophorus damnificus infections primarily focus on reducing snail populations in ponds. Other aquatic snail species are also commonly associated with commercial catfish ponds, although little is known about their contributions to trematode infections in catfish. In the summer of 2014, 804 snails Biomphalaria havanensis (synonym: Biomphalaria obstructa) were collected from a single commercial catfish pond and screened for trematode infections. Seven of these snails (0.81%) were actively releasing cercariae identified molecularly as Bolbophorus damnificus. These cercariae were subsequently used in infectivity trials with Channel Catfish Ictalurus punctatus fingerlings (5–8 cm). Seven days postchallenge, fish were examined histologically for the presence of metacercariae, which were present in 13 of 15 (86.67%) surviving fish. This is the first report of naturally occurring infections of Bolbophorus damnificus in another snail species.

Comparative susceptibility of Channel Catfish, Blue Catfish, and their hybrid cross to experimental challenge with Bolbophorus damnificus (Digenea: Bolbophoridae) cercariae.

The digenetic trematode Bolbophorus damnificus has been implicated in significant losses in catfish aquaculture since the late 1990s. The complex life cycle sequentially involves the American white pelican Pelecanus erythrorhynchos, the marsh rams horn snail Planorbella trivolvis, and Channel Catfish Ictalurus punctatus. Research supports anecdotal reports from the industry, suggesting that the hybrid of Channel Catfish×Blue Catfish I. furcatus is less susceptible to disease agents that have been historically prohibitive to Channel Catfish production, namely the gram-negative bacteria Edwardsiella ictaluri and Flavobacterium columnare, as well as the myxozoan parasite Henneguya ictaluri. This current research compared the susceptibility of Channel Catfish, Blue Catfish, and their hybrid cross to an experimental challenge by B. damnificus. Fish were exposed to 0, 100, 200, and 400 B. damnificus cercariae per fish, and the numbers of metacercariae per fish were determined 14 d postchallenge. Metacercariae were recovered from all challenged fish. There were no significant differences among fish groups challenged with the same dose, suggesting Channel and Blue Catfish and their hybrid are comparably susceptible to B. damnificus infection. As such, it is recommended that producers raising hybrid catfish remain diligent in controlling populations of the snail intermediate host to prevent production losses attributed to B. damnificus, especially when loafing pelicans have been observed at the aquaculture operation.

Longevity of Bolbophorus damnificus Infections in Channel Catfish

The digenean Bolbophorus damnificus infects commercial channel catfish Ictalurus punctatus, causing mortality, lower feed consumption, and reduced growth in surviving fish. The purpose of this study was to determine the length of time for which B. damnificus prodiplostomulum metacercariae (juvenile trematode stage that infects fish) would remain viable (parasite appearing to be intact or exhibiting movement) in channel catfish. Fish (n = 210) were infected with molecularly confirmed B. damnificus cercariae harvested from naturally infected marsh rams-horn snails Planorbella trivolvis. During the first sampling (at 20 d postinfection), 8.3 +/- 3.6 metacercariae/fish (mean +/- SD) were found in the host muscle and visceral organs. The channel catfish were then acclimated to a water temperature of either 18 degrees C or 28 degrees C. After 11 months, 6.8 +/- 3.5 and 5.9 +/- 3.0 metacercariae/fish were found in groups held at 18 degrees C and 28 degrees C, respectively. The mean number of parasites per fish did not significantly differ between fish held at the two temperatures and did not significantly decline over time at either temperature. Fish examined from 13 to 30 months postinfection all contained viable metacercariae that were morphologically and molecularly identified as B. damnificus. At 18 months, 12 metacercariae (of which 11 were intact and 10 displayed movement) were found in the one fish sampled; at 30 months, the last fish sampled contained three intact metacercariae (one displayed slight movement). Our results indicate that B. damnificus metacercariae can remain viable in channel catfish for at least an 18-30-month production cycle during which they have the potential to affect fish growth; in addition, infected fish may serve as intermediate hosts for these metacercariae for at least 2.5 years postinfection.

A Duplex Real-Time Polymerase Chain Reaction Assay for Differentiation between Bolbophorus Damnificus and Bolbophorus Type II Species Cercariae

A duplex quantitative real-time polymerase chain reaction (qPCR) assay was developed to differentiate between Bolbophorus damnificus and Bolbophorus type II species cercariae. Both trematode species are prevalent throughout the commercial catfish industry, as both infect the ram's horn snail, Planorbella trivolvis, which is commonly found in catfish ponds. Identification of cercaria to species is important in catfish disease challenge experiments, as only B. damnificus has been shown to have negative impacts on channel catfish. Oligonucleotide primers and fluorescence resonance energy transfer hydrolysis probes were designed to amplify the 18S small subunit ribosomal DNA gene of each species. The quantification cycle indicative of the number of cercariae in the sample prep was determined, and standard curves correlating to cercaria numbers were established. For both species, the assay was found to be highly repeatable and reproducible, with a linear dynamic range covering 7 orders of magnitude. The sensitivity limit of the assay was approximately 1/256th of a cercaria, regardless of species, and there was no remarkable interference between the 2 assays when run simultaneously within the same reaction. In a field study, identification of cercaria by the duplex real-time qPCR assay was in complete agreement with previously established end-point PCR protocols, demonstrating the assay to be a more rapid, quantifiable means of parasite identification.

EXPERIMENTAL BOLBOPHORUS DAMNIFICUS (DIGENEA: BOLBOPHORIDAE) INFECTIONS IN PISCIVOROUS BIRDS

In order to determine potential definitive hosts of the digenetic trematode, Bolbophorus damnificus, two American White Pelicans (Pelecanus erythrorhynchos), two Double-crested Cormorants (Phalacrocorax auritus), two Great Blue Herons (Ardea herodias), and two Great Egrets (Ardea alba) were captured, treated with praziquantel, and fed channel catfish (Ictalurus punctatus) infected with B. damnificus metacercariae. Patent infections of B. damnificus, which developed in both American White Pelicans at 3 days postinfection, were confirmed by the presence of trematode ova in the feces. Mature B. damnificus trematodes were recovered from the intestines of both pelicans at 21 days postinfection, further confirming the establishment of infection. No evidence of B. damnificus infections was observed in the other bird species studied. This study provides further evidence that Double-crested Cormorants, Great Blue Herons, and Great Egrets do not serve as definitive hosts for B. damnificus.

Biomphalaria havanensis Identified as a Potential Intermediate Host for the Digenetic Trematode Bolbophorus damnificus

AbstractThe digenetic trematode Bolbophorus damnificus has been associated with mortalities in commercial channel catfish Ictalurus punctatus in the Mississippi Delta. In the life cycle of B. damnificus, the only confirmed first intermediate host is the ram's horn snail Planorbella trivolvis. Recently, the exotic snail Biomphalaria havanensis has been isolated in several channel catfish ponds in the Mississippi Delta. The aim of this study was to determine whether this invasive snail species could also serve as a first intermediate host in the B. damnificus life cycle. Bolbophorus damnificus ova were collected from an American white pelican Pelecanus erythrorhynchos that had been artificially infected with B. damnificus metacercariae; the ova were then introduced into an aquarium with parasite‐negative B. havanensis. Bolbophorus damnificus cercariae (confirmed by polymerase chain reaction) were detected in B. havanensis 45 d after exposure to B. damnificus ova. The snails continued to shed B. damnificus cercariae throughout the 80‐d postexposure examination period. Before this research, the only reported natural B. damnificus infection of snails involved P. trivolvis. This study indicates that the range of snail hosts is broader than previously suspected. A survey should be implemented to identify additional snail species that can serve as hosts for B. damnificus. Further research should determine whether B. havanensis is a natural host for B. damnificus, and if so the prevalence of B. havanensis in commercial channel catfish ponds should be assessed.

A Novel Henneguya Species from Channel Catfish Described by Morphological, Histological, and Molecular Characterization

Channel catfish Ictalurus punctatus from a commercial farming operation in the Mississippi Delta were submitted for examination for the presence of infection by the trematode Bolbophorus damnificus. The fish were instead found to possess skin nodules suggestive of Henneguya pellis, a species previously described in the blue catfish I. furcatus. Despite the dermal location and distribution of lesions, morphological characteristics of the myxospores were inconsistent with H. pellis. Spores possessed a lanceolate spore body 15.4 +/- 1.5 microm (mean +/- SD; range = 12.2-19.3 microm) in length and 5.5 +/- 0.6 microm (range = 4.5-6.8 microm) in width in valvular view, and 4.7 +/- 0.2 microm (range = 4.2-5.0 microm) in width in sutural view. Polar capsules were pyriform and unequal in both length and width and contained polar filaments with six coils. Polar capsules measured 6.1 +/- 0.8 microm (range = 4.0-7.9 microm) long and 1.7 +/- 0.3 microm (range = 1.0-2.2 microm) wide. The caudal appendages were 50.5 +/- 8.3 microm (range = 34.8-71.4 micorm) long and the total length of the spore was 65.9 +/- 8.6 microm (range = 48.2-90.0 microm). The "blister like" plasmodia were round or ovoid, up to 2 mm in diameter, and randomly distributed throughout the epidermis of the fish. Histologically, plasmodia were confined to the dermis and elicited no inflammatory reaction from the fish. A blast search of the 18S small subunit rDNA sequence obtained by polymerase chain reaction amplification resulted in no identical sequence matches but indicated a close relationship to H. gurlei, H. ictaluri, and H. exilis. The unique host record, spore morphology, and novel genetic sequence derived from this isolate lead us to propose this isolate as a novel species, H. sutherlandi.

Evaluating Pond Shoreline Treatments of Slurried Hydrated Lime for Reducing Marsh Rams‐Horn Snail Populations

AbstractTrematode parasites can cause massive infections in commercially raised fish. The most promising approach for the control of these infections is the reduction or elimination of snails that serve as vectors for the trematodes. A recent approach, the application of high concentrations of slurried hydrated lime (SHL) or copper sulfate pentahydrate (CSP) along pond margins (shoreline treatment), has shown promise in reducing populations of the marsh rams‐horn snail Planorbella trivolvis (the snail vector of Bolbophorus damnificus and Clinostomum marginatum) in experimental ponds. While CSP has been shown to effectively reduce snail numbers, treatment efficacy and application methods using SHL have not been well defined. Four SHL treatments were evaluated for their ability to kill marsh rams‐horn snails in experimental units designed to mimic commercial aquaculture ponds. The treatments were applied at water temperatures of 75–79°F (24–26°C), total alkalinity of 137–257 mg CaCO3/L of water, and total hardness of 86–120 mg CaCO3/L. All tested SHL applications reduced snail numbers; however, the applications of 100 lb of hydrated lime per 100 linear feet (3‐ft swath) and 175 lb per 100 ft (6‐ft swath) were the most effective, resulting in 97.2% and 98.3% reductions in snail survival, respectively.

Cercariae of Bolbophorus damnificus and Bolbophorus sp. with Notes on North American Bolbophorids

Single-species and dual infections of Bolbophorus damnificus and a second cryptic species of Bolbophorus were distinguished in marsh rams-horn snails, Planorbella trivolvis, from aquaculture ponds in Mississippi, U.S.A. The cercariae of both B. damnificus and Bolbophorus sp. are described and distinguished using differences in body length, tail stem length, intestinal primordia, and integument spine patterns.

Effect of Sublethal Exposure to the Trematode Bolbophorus spp. on the Severity of Enteric Septicemia of Catfish inChannel Catfish Fingerlings

The digenetic trematode Bolbophorus damnificus has been implicated as a cause of mortalities and reduced production in farmed channel catfish Ictalurus punctatus in northwestern Mississippi. Field observations indicate that infection can exacerbate losses from common bacterial diseases, such as enteric septicemia of catfish (ESC), which is caused by Edwardsiella ictaluri. The interaction of concurrent infections with Bolbophorus spp. and E. ictaluri was investigated using three replicates of four experimental treatments. Trematode infections were established by placing fingerlings for 24 h in triplicate static tanks containing marsh rams-horn snails Planorbella trivolvis shedding Bolbophorus cercariae at a rate of 770 ± 82 (mean ± SE) per 24-h period. Unexposed fish were maintained in three tanks under similar conditions. From each tank, trematode-infected or noninfected fish were transferred to six aquaria (30 fish/aquarium). Three aquaria from each replicate treatment tank received 7.5 × 105 colony-forming units (CFU) of E. ictaluri/mL of water for 30 min (Bolbophorus–ESC and ESC-only groups). Fish in the remaining three aquaria were not exposed to E. ictaluri and served as Bolbophorus-only and negative control groups. No mortalities were observed in the Bolbophorus-only and negative control groups. Twenty-one days after exposure to E. ictaluri, the percent cumulative mortalities were 84.1 ±16.2% in the Bolbophorus–ESC treatment and 45.9 ± 3.2% in the ESC-only treatment. Mortalities were significantly different between the two groups (P = 0.0161). In a second study, fingerlings were challenged with E. ictaluri 28 d after trematode exposure; 21 d later, no differences in cumulative percent mortalities were observed between trematode-infected (21.5 ± 1.7%) and trematode-negative (17.8 ± 4.01%) fish. These studies show that sublethal Bolbophorus infection increases mortalities from E. ictaluri when exposure occurs simultaneously but not when ESC infection occurs 28 d after trematode exposure.

Bolbophorus damnificus n. sp. (Digenea: Bolbophoridae) from the channel catfish Ictalurus punctatus and American white pelican Pelecanus erythrorhynchos in the USA based on life-cycle and molecular data

The common pathogenic prodiplostomulum metacercaria in the flesh, mostly near the skin, of pond-produced channel catfish Ictalurus punctatus has been demonstrated to be Bolbophorus damnificus Overstreet & Curran n. sp. The catfish acquires the infection from the snail Planorbella trivolvis, the only known first intermediate host, and the species is perpetuated through the American white pelican Pelecanus erythrorhynchos, as confirmed by experimental infections with nestling and dewormed adult pelican specimens in conjunction with molecular data. It differs from the cryptic species Bolbophorus sp., also found concurrently in the American white pelican, by having eggs 123-129 microm rather than 100-112 microm long and consistent low values for nucleotide percentage sequence similarity comparing COI, ITS 1/2, 18S rRNA and 28S rRNA fragments. Bolbophorus sp. is comparable but most likely distinct from B. confusus (Kraus, 1914), which occurs in Europe and has eggs 90-102 microm long. Its intermediate hosts were not demonstrated. The adults of neither of the confirmed North American species of Bolbophorus were encountered in any bird other than a pelican, although several shore birds feed on infected catfish, and B. damnificus can survive but not mature when protected in the mouse abdominal cavity. B. ictaluri (Haderlie, 1953) Overstreet & Curran n. comb., a species different from B. damnificus, is considered a species inquirenda.